(1) Field of the Invention
The present invention relates to method and apparatus for controlling the fuel injection amount and timing for a Diesel engine and more particularly to a method of controlling the fuel injection amount and timing for a Diesel engine during the running environment where the change in altitude and/or the change in atmospheric pressure occurs.
(2) Description of the Prior Art
In the diesel engine according to the prior art, when operating the engine, maximum fuel injection amount is determined in accordance with the engine speed and excessive fuel injection by the operation of an accelerator pedal can be prevented, thus in turn preventing black smoke from being generated.
However, in the environment where the atmospheric pressure is low such as at high elevations, the similar control for the Diesel engine as in the case of low geographical places or normal environmental places caused the black smoke to be generated in the engine operating or running at high elevations.
In order to overcome the problem mentioned above, a correction was made so as to reduce the maximum fuel injection amount which was an upper limit of the fuel injection amount at high elevations by using an atmospheric pressure sensor which changes its output in accordance with the atmospheric pressure
One of the shortcomings of the atmospheric pressure sensor was that because of its method of operation which involved measuring the amount of a mechanical displacement due to the difference between atmospheric pressures inside and outside of a measuring unit such as a diaphragm valve, with the result that a relatively large space is required for it. Moreover, in the technique according to the prior art, not only is the measuring accuracy insufficient but also the mechanical portions and mechanically operating portions were often subject to troubles and failures.
In the intake or suction air pressure sensor of a semiconductor strain gauge type for detecting air pressure, which is proportional to the atmospheric pressure, there were problems such as securing sufficient mounting space without complicating the unit low durability good and the cost of the unit became expensive. and high cost mechanically operating portions but having a long durability and a relatively simple construction has been desired heretofore. Moreover, an atmospheric pressure measuring unit which can be commonly used as other measuring units that is also light in weight and small enough to carry on a car has been desired.